This invention relates to a dual containment channel for fluids. The invention has application with any type of fluid and many types of gases which must be conveyed in quantity from one place to another. However, this invention has particular utility in the conveyance of hazardous or toxic fluids such as are often found in heavy industrial facilities. The channel segments of the type referred to in this application may be constructed of various materials and according to various processes to support light, medium or heavy loads. In the particular embodiment described in this application, the channel segments are cast of "polyester concrete", a concrete aggregate material containing quartz and inert mineral fillers bonded with polyester resin.
Typically, the drainage channel segments are cast in relatively short lengths of one meter. The channels may be non-sloping, or if sloping, with a bottom slope of, for example, 0.6 percent from one end to the other. When sloping drainage channel segments are used, the channel is formed by using cast channel segments having successively higher walls so that when put in the proper order in a trench with their up surface horizontal, they collectively form a channel run having a predetermined slope.
Insofar as is known, drainage channels of the general type described above have heretofore been used for open drainage, i.e., the drainage of parking lots, airports and driveways and certain interior fluid drainage applications wherein a slotted grate is positioned in the open top of the drainage channels to permit drainage into the channel from a surrounding, relatively flat surface.
Hazardous fluids cannot be routinely conveyed in open top drainage channels, but instead in enclosed pipes or conduits. Recognizing that such pipes and conduits can leak because of manufacturing defects, excessive pressure, corrosion or other reasons, prior art dual containment systems generally involve the placement of a relatively small fluid carrying closed-wall conduit within a larger closed-wall conduit which does not carry fluids except in the event of a leak of liquid carried by the inner conduit. The smaller conduit is supported by resting directly on the lower, inner wall of the outer conduit.
While the above-described system will perform adequately to prevent leakage of hazardous fluids into the environment from the inner conduit, repairing the leak in the inner conduit is expensive and time consuming. In many cases, the inner and outer conduits are hundreds of feet long and are formed either of seamless extruded conduit or conduit formed of relatively long segments. Since both conduits are closed-wall, the outer conduit must be penetrated to determine the location of the leak in the inner conduit. In some cases, the inner conduit must be disconnected and physically removed from the outer conduit. In other instances, the outer conduit must be penetrated at intervals along its length to determine the position of the leak. Even then, further damage to the outer conduit must take place in order to remove and/or repair the inner conduit and return it to use.
The invention described in this application provides all of the safety and security of a dual wall containment system formed of inner and outer closed-wall conduits, while permitting easy access to the inner conduit to determine the location of a leak for repair. Furthermore, in accordance with one embodiment of the invention, leakage from an inner conduit can be drained away to a remote location for storage or disposal.